Electric motor driven tool for orthopedic impacting

ABSTRACT

An orthopedic impacting tool comprises a motor, a linear motion converter, an air chamber, a compression piston, an impacting element, an anvil element, and a broach adapter. The compression piston may cause the impacting element to apply controlled force on a broach adapter to create a precise opening for subsequently disposing a prosthesis in a patient. The tool allows forward or backward impacting for expanding the size or volume of the opening or for facilitating removal of the broach and tool from the opening. A force adjustment control of the tool allows a user to increase or decrease the impact force. A light source and hand grips improve ease of operation of the tool.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/857,385 entitled “Electric Motor Driven Tool for OrthopedicImpacting,” filed Dec. 28, 2017, which is a continuation of U.S. patentapplication Ser. No. 14/250,102 entitled “Electric Motor Driven Tool forOrthopedic Impacting,” filed Apr. 10, 2014 (now U.S. Pat. No.9,901,354), which is a divisional of U.S. patent application Ser. No.12/980,329 entitled “Electric Motor Driven Tool for OrthopedicImpacting” filed Dec. 29, 2010 (now U.S. Pat. No. 8,695,726). All aboveidentified applications are hereby incorporated by reference in theirentireties.

FIELD

The present disclosure relates to electric tools for impacting inorthopedic applications, and, more particularly, to an electric motordriven tool for orthopedic impacting that is capable of providingcontrolled impacts to a broach, chisel, or other device for creating anopening in an area (in a bone structure, for example) to securelyreceive prosthesis within the area.

In the field of orthopedics, prosthetic devices such as artificialjoints, are often implanted or seated in a patient's body by seating theprosthetic device in a cavity of a bone of the patient. The cavity mustbe created before the prosthesis is seated or implanted, andtraditionally, a physician may remove worn, excess, or diseased bonestructure from the area in which the cavity will be formed, and thendrill and hollow out a cavity along the medullar canal of the bone. Aprosthesis usually includes a stem or other protrusion that serves asthe particular portion of the prosthesis that is inserted into thecavity.

To create such a cavity, a physician may use a broach, which broachconforms to the shape of the stem of the prosthesis. Solutions known inthe art include providing a handle with the broach, which handle thephysician may grasp while hammering the broach into the implant area.Unfortunately, this approach is clumsy and unpredictable as beingsubject to the skill of the particular physician. This approach almostwill always inevitably result in inaccuracies in the location andconfiguration of the cavity. Further, this approach carries with it therisk that the physician will damage bone structure in unintended areas.

Another technique for creating the prosthetic cavity is to drive thebroach pneumatically, that is, by compressed air. This approach isdisadvantageous in that it prevents portability of an impacting tool,for instance, because of the presence of a tethering air line, air beingexhausted from a tool into the sterile operating field and fatigue ofthe physician operating the tool. Further this approach, as exemplifiedin U.S. Pat. No. 5,057,112 does not allow for precise control of theimpact force or frequency and instead functions very much like ajackhammer when actuated. Again, this lack of any measure of precisecontrol makes accurate broaching of the cavity more difficult.

Another disadvantage of tools known in the art is the accumulation offluids, such as body fluids or moisture, on handgrips of such toolsduring prolonged periods of use. For example, difficulty of operation ofa broach impacting device known in the art may increase during asurgical procedure as handgrips may become saturated with bodily fluidsand thus the physician's hold on such a prior art device may becomeimpaired.

Consequently, there exists a need for an impacting tool that overcomesthe various disadvantages in the prior art.

In view of the foregoing disadvantages of the prior art, an electricmotor-driven orthopedic impacting tool configured to include all theadvantages of the prior art, and to overcome the drawbacks inherenttherein is provided. The tool may be used by orthopedic surgeons fororthopedic impacting in for example hips, knees, and shoulders. The toolis capable of holding a broach, chisel, or other device and gentlytapping the broach, chisel or other device into the cavity withcontrolled percussive impacts, resulting in a better fit for theprosthesis or the implant. Further, the control afforded by such anelectrically manipulated broach, chisel, or other device allowsadjustment of the impact settings according to a particular bone type orother profile of a patient. The tool additionally enables proper seatingor removal of the prosthesis or the implant into or out of an implantcavity.

In an embodiment, an electric motor-driven orthopedic impacting toolcomprises a control unit, a housing, a linear motion converter, at leastone reducing gear, an impacting element (also referred to herein as astriker), an air chamber, a compression piston, and a force adjustmentcontrol means (hereinafter referred to as ‘control means’). The tool mayfurther include a motor, an LED, a handle portion with at least onehandgrip for comfortable gripping the tool, a broach adapter, a battery,a feedback system and a nose-piece for the broach adapter. At least someof the various components are preferably contained within the housing.The tool is capable of applying cyclic impact forces on a broach,chisel, or other device, or an implant and of finely tuning impact forceto a plurality of levels of impact force.

In an embodiment, the tool further comprises a control means, whichmeans includes a force adjustment element, and which element may controlthe impact force and avoid damage caused by uncontrolled impacts.

The tool further comprises an anvil element, which anvil elementincludes both a forward and rearward point of impact and a guide thatconstrains the striker to move in a substantially axial direction. Inoperation, the movement of the striker along the guide of the anvilelement continues in either a forward or rearward direction until thestriker hits the point of impact. As used in this context, “forwarddirection” connotes movement of the striker toward a broach or patient,and “rearward direction” connotes movement of the striker away from thebroach or chisel or patient. If the impact point is at the front of thetool, i.e., in a forward direction, the impact causes the percussiveforce to be transmitted to a broach or chisel, pushing it further intothe cavity. If the impact point is at the rear of the tool, thepercussive force tends to pull the broach or chisel out of the cavity.The selectivity of either bidirectional or unidirectional impactingprovides flexibility to a surgeon in either cutting or compressingmaterial within the implant cavity, in that the choice of materialremoval or material compaction is often a critical decision in asurgical procedure. The impact point may be in the form of a plate thatis disposed at an end or each end of the anvil element.

The tool is further capable of regulating the frequency of the striker.By regulating the frequency of the striker, the tool may impart agreater total time-weighted percussive impact, while maintaining thesame impact magnitude. This allows for the surgeon to control thecutting speed of the broach or chisel. For example, the surgeon maychoose cutting at a faster rate (higher frequency impacting) during thebulk of the broach or chisel movement and then slow the cutting rate asthe broach or chisel approaches a desired depth.

A user may firmly hold the tool by the handle portion and utilize lightemitted by the LED to light up a work area and accurately position thebroach, chisel, or other device on a desired location on the prosthesisor the implant. The reciprocating movement imparted on broach, chisel,or other device causes tapping of the implant and/or broach, chisel, orother device and thereby enables proper seating or removal of aprosthesis or implant into or out of an implant cavity, or controlledimpacting of a broach, chisel, or other device to create or shape animplant cavity. The tool may also include a feedback system that warnsthe surgeon, when a bending or off-line orientation beyond a certainmagnitude is detected at a broach, chisel, or other device/implantinterface.

These together with other aspects of the present disclosure, along withthe various features of novelty that characterize the presentdisclosure, is pointed out with particularity in the claims annexedhereto and forms a part of this present disclosure. For a betterunderstanding of the present disclosure, its operating advantages, andthe specific objects attained by its uses, reference should be made tothe accompanying drawing and descriptive matter in which there areillustrated exemplary embodiments of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The advantages and features of the present invention will become betterunderstood with reference to the following detailed description andclaims taken in conjunction with the accompanying drawings, wherein likeelements are identified with like symbols, and in which:

FIG. 1 shows a perspective view of an orthopedic impacting tool, inaccordance with an exemplary embodiment of the present disclosure;

FIG. 2 shows a perspective view of a compression piston compressing airagainst a striker of an orthopedic impacting tool, in accordance with anexemplary embodiment of the present disclosure;

FIG. 3 shows a striker releasing and striking an anvil element, inaccordance with an exemplary embodiment of the present disclosure;

FIG. 4 shows a compression piston of an orthopedic impacting toolreturning from a forward position and compressing air on the forwardside of a striker, in accordance with an exemplary embodiment of thepresent disclosure;

FIG. 5 shows a striker of an orthopedic impacting tool moving rearward,in accordance with an exemplary embodiment of the present disclosure;and

FIG. 6 shows a striker of an orthopedic impacting tool impacting a rearanvil impact plate, in accordance with an exemplary embodiment of thepresent disclosure.

Like references numerals refer to like parts throughout the descriptionof several views of the drawings.

LIST OF ELEMENTS IN FIGURES

1 Broach Adapter

2 Anvil antirotation element

3

4 Striker

5 Forward Air Chamber

6 Compression Piston

7 Gear Reducer

8 Motor

9 Gear Reducer

10 Detent

11 Forward Striker Air Chamber

12 Linear Motion Converter

13 Broach Quick connect

14 Anvil

15 Forward anvil impact plate

16 Rear anvil impact plate

17 Rear air Chamber

18

19 Air Passageway

DETAILED DESCRIPTION OF THE DISCLOSURE

The best mode for carrying out the present disclosure is presented interms of its preferred embodiment, herein depicted in the accompanyingfigures. The preferred embodiments described herein detail forillustrative purposes are subject to many variations. It is understoodthat various omissions and substitutions of equivalents are contemplatedas circumstances may suggest or render expedient, but are intended tocover the application or implementation without departing from thespirit or scope of the present disclosure.

The terms “a” and “an” herein do not denote a limitation of quantity,but rather denote the presence of at least one of the referenced items.

Referring now to FIGS. 1-6, the present disclosure provides an electricmotor-driven orthopedic impacting tool with controlled percussiveimpacts. The tool includes the capability to perform single or multipleimpacts as well as impacting of variable speeds, forces and frequencies.The impact force can be tuned to one of a variety of levels by settingthe impact force electronically.

The tool includes a housing. The housing securely covers and holds aplurality of components of the tool. In an embodiment, the housingcontains a motor, at least one reducing gear, a linear motion converter,a compression chamber, an impacting element (alternately referred to asa striker), a force or impact adjustment control means (hereinafterreferred to as ‘control means’), and an anvil element with a forwardimpact plate and a rearward impact plate (which impact plates may bepart of the anvil, for example).

The tool further may include a handle portion with at least one handgrip for comfortable and secure holding of the tool while in use, abroach adapter, a battery, and a positional sensor, a directionalsensor, and/or a torsion sensor. The tool may further comprise alighting element such as an LED to provide light in the work area inwhich a user employs the tool. The broach adapter can be coupled to ananvil, of the anvil element for example, through a quick connectmechanism at the end of the tool that is directed at a patient when thetool is in use.

In an embodiment, and referring now to FIG. 1, the linear motionconverter comprises a slider crank mechanism 12, which slider crank isoperatively coupled to the motor 8 and reducing gears 7 and 9. The toolfurther comprises an air chamber 5, 17 that accepts a compression piston6 with a first end and a second end, which compression piston 6 isactuated by the linear motion converter 12. As the compression pistonwill have a smaller longitudinal dimension than the air chamber thatcontains the piston, it will be apparent that an air mass will bepresent at either end of the compression piston while the compressionpiston is within the air chamber. Hereinafter, the air mass disposedbetween the head of compression piston and the striker will be referredto as the “forward air chamber portion,” or “forward air chamber” 5, andthe air mass disposed between the end of the compression piston that isproximate to the linear motion converter and the motor of the tool willbe referred to as the “rear air chamber portion,” or “rear air chamber”17.

In an embodiment of the present disclosure the motor of the tool, suchas for example a voice coil motor, causes the linear motion converter tomove the compression piston until sufficient pressure is built withinthe forward air chamber 5 that is disposed between the forward end ofthe compression piston and the rearward end of the striker 4 to overcomethe inertia and frictional force that holds the striker 4 in a position.Once this sufficient pressure is reached, the force of the air pressureaccelerates the striker 4, which striker 4 slides axially down a cavityinternal to the tool housing and strikes the forward anvil impact plate15. The resultant force is communicated through the anvil 14 that isproximate to the impact plate 15 and, optionally, through the broachadapter 1 (which adapter will be described in more detail below) towhich a broach, chisel, or other device for seating or removing animplant, or prosthesis may be attached.

As the compression piston 6 continues through its stroke it movestowards the rear direction, compressing the air mass in the rear airchamber 17. This air mass may be communicated through an air passagewayto the front side of the striker 4, creating a returning force on thestriker 4, which returning force causes the striker 4 to move in a reardirection, i.e., a direction away from the point of impact of thestriker the forward anvil impact plate 15. The striker continues to moveuntil it impacts the rear anvil impact plate 16. Striking the rearimpact plate creates a rear directed force on the anvil 14. In the eventthat a broach adapter 1 is attached to the anvil 14, the force iscommunicated through the broach adapter 1 to which the broach, chisel,or other device for seating or removing an implant, or prosthesis isattached. Thus in one complete cycle, a forward and rear directedimpacting force can be applied on the broach, chisel, or other device,or implant/prosthesis.

In an embodiment, the compression piston preferably has a cavity on thehead thereof, which cavity creates pressure during the return stroke ofthe piston, which pressure causes the front end of the striker to moveaway from the forward anvil impact plate impact the rearward point ofimpact of the anvil element. It will be apparent that the strikerimpacting the rear anvil impact plate will communicate a negative forceto the front of the anvil (and broach, chisel, or other device), whichnegative force will move the broach, chisel, or other device away fromthe location of impact in a surgical area.

The slider crank embodiment of the tool facilitates controlledcontinuous impacting of the striker and anvil. For such continuousimpacting, after causing compression by the compression piston, theslider crank returns to the bottom of its stroke, which return releasespressure on the striker and, in the above-described embodiment whereinthe piston comprises a cavity on the head thereof, may pressurize thefront of the striker, causing the striker to return to its initial restposition.

For a single stroke, the linear motion converter (such as the slidercrank described herein) will stop at or near the rear position, thusreleasing the forward pressure on the striker and allowing the strikerto return it to its starting position in readiness for another stroke.In this operational mode, a user may cause the tool to impactselectively (as opposed to repeatedly), thus allowing further control ofthe impacts and the creation or shaping of the surgical area, forexample.

A positional sensor, coupled operatively to the control unit may beprovided to assist in regulating a preferred positional cyclic operationof the linear motion converter. For example, the control unit may causethe slider crank to come to rest at or near the fully back position inreadiness to generate pressure for the next impact upon receiving asignal from the positional sensor that the slider crank has reached thebottom dead center position. In another embodiment, the control unit maybe directly coupled to the linear motion converter for initiating andceasing operation of the linear motion converter.

The control unit is further capable of operating the force control meansfor selectively tuning the amount of impact force per cycle. Bycontrolling the impact force the tool can avoid damage caused byuncontrolled impacts or impacts of excessive force. For example, a usermay reduce the impact setting in the case of an elderly patent withosteoporosis, or may increase the impact setting for more resilient orintact athletic bone structures.

The control unit may also control the force of impacting by modulatingthe speed of advancing (forward directional travel) and/or the speed ofretraction (rearward directional travel) of the compression piston. Itwill be apparent that the modulation of speed of the compression pistonwill affect the buildup of pressure for forward and rearward directionaltravel of the striker. For example, where the speed of the forwarddirection of the piston is relatively high, and the speed of therearward direction of the piston is relatively low, the velocity of thestriker in the forward direction will be much higher, causing theimparted percussive impact of the striker to be greater in the forwarddirection of the piston and striker. This modulation of the speed of thepiston in the forward and rearward direction allows a user to create agreater impacting force, when so desired (e.g., to create a surgicalarea) or a greater rearward force, to facilitate removing a broach,chisel, or other device from the surgical area, for example. In theinstance where the forward and rear velocities are the same, the toolallows for bidirectional movement of the broach, chisel, or other deviceduring operation, which creates a very efficient technique for machiningthe cavity.

The motor of the tool may be configured to assist particularly with suchmultidirectional impacting. In an embodiment, the motor may operateunder pulse-width modulation for rearward striking and may operate underfull or continuous speed for forward striking of the striker. In suchoperation, the broach, chisel, or other device attached to the tool mayundergo near forward only motion, which operation will facilitate thecreation of an implant seat. Alternatively, the motor may operate underpulse-width modulation for forward striking and may operate under fullor continuous speed for rearward impacting, which operation can createan extraction motion useful for dislodging a broach, chisel, or otherdevice that has become stuck or removing an implant.

In a further embodiment, the tool comprises a positional sensor, such asan anvil positional sensor that may be operatively coupled to thecontrol unit of the striker of the tool. This positional sensor iscapable of determining whether the operator is pushing or pulling on thetool. For instance, the sensor may determine such pushing or pullingbased upon the position of the broach-holding adapter or anvil. Thisdetermination can have the effect that when a user is exerting force onthe tool in a particular direction the impacting of the striker isaccordingly adjusted. For example, if the sensor determines that theuser is pushing on the tool or is pushing the tool against an object,that sensor can cause the striker to impact in a forward direction. Ifthe sensor determines that the user is pulling on the tool, that sensormay cause the striker to impact in a rearward direction or may cause apulling force to be exerted on the striker by way of the cycling of theslider crank.

The tool may further comprise a lighting element, and, in an embodiment,the lighting element may comprise an LED arrangement, which lightingelement may be capable of illuminating a user's work area. In anembodiment, the LED may be disposed on the housing of the tool and maybe oriented toward a patient's body or surgical cavity.

The tool may further comprise a plate or other flat surface at the endof the tool that is distal to the surgical area, which plate may allow auser to apply selective manual pressure on a broach, chisel or otherdevice, or a surgical implant as dictated by surgical or physicalconditions. For instance, if a broach is firmly lodged within a cavitysuch that the operation of the tool would not remove the broach, theuser may manually tap on the plate to dislodge the broach.

The tool may further comprise a torsion sensor, which torsion sensor maybe capable of determining a lateral or deviating force or movement ofthe tool, such that if the tool is sensed to deviate from apre-determined magnitude at the broach/implant interface, a signal mayemit to notify the user of such deviation. In this manner and otherwise,the tool facilitates consistent axial broaching and implant seating.

In a further embodiment, the broach adapter may comprise a parallel4-bar arrangement. In this embodiment, the adapter may receive a broachfor anterior or posterior joint replacement. The parallel 4-barmechanism of the adapter may facilitate receiving and orienting thebroach in a variety of positions, such as in a centered position, or inan offset left or right position. The adapter will maintain the broachin an orientation that is parallel or co-linear to the body of the tooland the striker. The broach adapter may also comprise clamps, a vice, orany other fastener that may securely hold the broach, chisel, or otherdevice, during operation of the tool.

The tool may further comprise handgrips disposed on the housing of thetool, which handgrips may include a rubberized or other tacky coatingremovably disposed thereon. Such coating facilitates comfortableoperation of the tool and improves the user's hold on the tool forincreased control thereof and reduced fatigue during operation of thetool.

In use, a user such as a surgeon firmly holds the tool by the handlegrip or grips and utilizes light emitted by the LED to illuminate a workarea and accurately position a broach, chisel or other device that hasbeen attached to the tool on a desired location on the prosthesis orimplant. The reciprocating movement imparted by the tool upon thebroach, chisel or other device causes tapping of the implant and therebyenables proper seating or removal of the prosthesis or the implant intoor out of an implant cavity. The warning system may alert the user inthe event that a bending moment above a certain magnitude is detected ata broach (or chisel or other device)/implant interface.

The tool disclosed herein provides various advantages over the priorart. It facilitates controlled impacting at a surgical site, whichminimizes unnecessary damage to a patient's body and which allowsprecise shaping of an implant or prosthesis seat. The tool also allowsthe user to modulate the direction and force of impacts, which improvesthe user's ability to manipulate the tool. The force control adjustmentof the impact settings allows a user to set the force of impactaccording to a particular bone type or other profile of a patient. Thetool thereby enables proper seating or removal of the prosthesis or theimplant into or out of an implant cavity.

The foregoing descriptions of specific embodiments of the presentdisclosure have been presented for purposes of illustration anddescription. They are not intended to be exhaustive or to limit thepresent disclosure to the precise forms disclosed, and obviously manymodifications and variations are possible in light of the aboveteaching. The exemplary embodiment was chosen and described in order tobest explain the principles of the present disclosure and its practicalapplication, to thereby enable others skilled in the art to best utilizethe disclosure and various embodiments with various modifications as aresuited to the particular use contemplated.

The invention claimed is:
 1. A surgical impacting tool, the toolcomprising: a motor; a piston operatively coupled to the motor; astriker; an adapter configured to hold a surgical implement; and aforward impact plate; a rearward impact plate; and a control unitconfigured to allow for percussive impacting of the striker on theforward impact plate and the rearward impact plate.
 2. The tool of claim1, wherein the impact of the striker on the forward impact plate isconfigured to cause the surgical implement held by the adapter to moveforward relative to a bone, and the impact of the striker on therearward impact plate is configured to cause the surgical implement heldby the adapter to move rearward relative to the bone.
 3. The tool ofclaim 1, further comprising an anvil configured to operatively couple tothe adapter such that the adapter is located in a forward portion of thetool.
 4. The tool of claim 1, wherein the piston is located in an airchamber of the tool.
 5. The tool of claim 4, wherein: the air chambercomprises a forward air chamber proximate to a first end of the piston,and a rear air chamber proximate to a second end of the piston; thecontrol unit is configured to direct the motor and thereby causemovement of the piston and to cause compression of air within theforward air chamber or compression of air within the rear air chamber;the striker is configured to move to impact the forward impact plateupon application of compressed air from the forward air chamber; and thestriker is configured to move to impact the rearward impact plate uponapplication of compressed air from the rear air chamber.
 6. The tool ofclaim 4, wherein: the air chamber comprises a forward air chamberproximate to a first end of the piston, and a rear air chamber proximateto a second end of the piston; the tool further comprises an airpassageway configured to communicate air from the air chamber to thestriker; the control unit is configured to direct the motor and therebycause movement of the piston from a first position to a second positionand cause compression of air within the forward air chamber; the strikeris configured to move to impact either the forward impact plate or therearward impact plate upon application of compressed air from the airchamber onto the striker such that the striker is configured to impart aforce upon the adapter in a first direction; and the motor is configuredto cause movement of the piston from the second position to the firstposition and thereby cause compression of air within the rear airchamber such that the compression of the air within the rear air chamberis communicated through the air passageway and onto the striker suchthat the compressed air communicated through the air passageway causesthe striker to impart a force upon the adapter in a second directionthat is opposite to the first direction.
 7. The tool of claim 1, furthercomprising a sensor configured to sense whether the tool is being pushedtoward an object or pulled away from an object; the control unit isconfigured to cause the striker to impart a greater force upon theforward impact plate and a lesser force on the rearward impact plate inresponse to the sensor sensing that the tool is being pushed toward theobject; and the control unit is configured to cause the striker toimpart a greater force upon the rear impact plate and a lesser force onthe forward impact plate in response to the sensor sensing that the toolis being pushed away from the object.
 8. The tool of claim 1, wherein avelocity of the striker is controllable by a speed at which the air iscompressed or decompressed.
 9. The tool of claim 1, further comprising adetent configured to retain the striker in a position.
 10. The tool ofclaim 9, wherein the control unit is configured to direct the motor tocause movement of the piston and compression of air within the airchamber such that when a pressure of the compressed air exceeds a forceof the detent the striker is caused to move from a first position to asecond position, thereby striking the forward impact plate or therearward impact plate.
 11. The tool of claim 9, further comprising aforce control element operatively coupled to the control unit andconfigured to at least one of change a speed at which the piston moveswithin the air chamber, and change a retention force of the detent. 12.A surgical impacting method, comprising: positioning, relative to bone,a surgical implement located at a forward portion of a surgicalimpacting tool; and electrically controlling a motor to cause percussivebone impacts of the surgical implement, the electric controlling of themotor to cause the percussive bone impacts comprising: electricallycontrolling the motor to cause a piston of the surgical impacting toolto move in a forward direction and thereby cause a striker of thesurgical impacting tool that is independently movable from the piston tomove in the forward direction and strike a first surface of the surgicalimpacting tool, the strike of the first surface causing the surgicalimplement to move forward relative to the bone, and electricallycontrolling the motor to cause the piston to move in a rearwarddirection and thereby cause the striker to move in the rearwarddirection and strike a second surface of the surgical impacting tool,the strike of the second surface causing the surgical implement to moverearward relative to the bone.
 13. The method of claim 12, wherein thefirst surface is on a first plate, and the second surface is on a secondplate.
 14. The method of claim 13, wherein the striker is disposed in acavity within the surgical impacting tool, the first surface is exposedto and faces the cavity, and the second surface is exposed to and facesthe cavity.
 15. The method of claim 12, wherein the piston is disposedin a chamber within the surgical impacting tool, the movement of thepiston in the forward direction causes compression of air within aforward portion of the chamber that is forward of the piston, and themovement of the piston in the rearward direction causes compression ofair within a rearward portion of the chamber that is to the rear of thepiston.
 16. The method of claim 15, wherein the striker is caused tomove in the forward direction in response to a pressure of the air inthe forward chamber exceeding a force holding the striker in positionduring the forward movement of the piston, and the striker is caused tomove in the rearward direction in response to a pressure of the air inthe rearward chamber exceeding a force holding the striker in positionduring the rearward movement of the piston.
 17. A surgical impactingmethod, comprising: positioning, relative to bone, a surgical implementlocated at a forward portion of a surgical impacting tool; electricallycontrolling a motor to cause a piston of the surgical impacting tool tomove in a forward direction within a chamber of the surgical impactingtool such that air is compressed within a forward portion of thechamber, wherein a striker of the surgical impacting tool that isindependently movable from the piston moves in the forward direction andstrikes a first surface of the surgical impacting tool in response to apressure of the air in the forward chamber exceeding a force holding thestriker in position during the forward movement of the piston, thestrike of the first surface causing the surgical implement to moveforward relative to the bone; and electrically controlling the motor tocause the piston to move in a rearward direction within the chamber suchthat air is compressed within a rearward portion of the chamber, whereinthe striker moves in the rearward direction and strikes a second surfaceof the surgical impacting tool in response to a pressure of the air inthe rearward chamber exceeding a force holding the striker in positionduring the rearward movement of the piston, the strike of the secondsurface causing the surgical implement to move rearward relative to thebone.
 18. The method of claim 17, wherein the first surface is on afirst plate, and the second surface is on a second plate.
 19. The methodof claim 18, wherein the striker is disposed in a cavity within thesurgical impacting tool, the first surface is exposed to and faces thecavity, and the second surface is exposed to and faces the cavity. 20.The method of claim 17, wherein the surgical impacting tool includes adetent that provides the force holding the striker in position duringthe forward movement of the piston and during the rearward movement ofthe piston.